OI 



LECTURE V. 



E L E c: T R O T O N U S . 



**■ An." and *' Kat." Influence of ether and chloroform. 

 Physiological and physical effects. The electro-mobility 

 of living matter. Relation between polarising and extra- 

 polar currents in nerve. Strength. Distance. Von 

 Fleischl's deflection. Action currents are counter - cur- 

 rents. Extrapolar effects in mammalian nerve. 



To-DA\'s chief experiment presents to you a demon- 

 stration of du Bois-Reymond's electrotonic currents, 

 commonly referred to by physiologists as Anelectro- 

 tonus and Katelectrotonus, but which I shall often 

 take the liberty of calling by the shorter and more 

 familiar workshop names of An. and Kat., and by 

 the still shorter pen-names A. and K. 



Experiment. (Fig. 44.) The nerve is resting 

 upon two pairs of unpolarisable electrodes, to receive 

 through p p' the polarising cicrrent from a battery (in 

 the present instance at the pressure of i '5 volt), and 

 to give off through e e' the electrotonic current which 

 will be indicated by the galvanometer. The polaris- 

 ing circuit is completed at will by the key, and it is 

 made to pass in one or the other direction in the 

 nerve by means of a reverser, rev.^ parallel with the 

 transparent scale of the galvanometer. 



^ For prolonged experiments a revolving key is used, by 

 which the polarising current is made through the nerve at 

 regular intervals in opposite directions. 



